Determination of mask fitting pressure and correct mask fit

1. A method for determining a mask-fit test pressure to be applied to a wearer's mask by ventilatory assistance apparatus, wherein the mask-fit pressure is adaptively dependent on a prior pressure treatment session of the wearer, said mask-fit test pressure not being significantly different than pressures encountered in normal use of the wearer during the prior treatment session, said mask-fit pressure being greater than a minimum pressure and less than a maximum pressure encountered during the prior treatment session.

2. The method of claim 1 , wherein the mask-fit test pressure is determined based on a prior use by comparing leak flow to a threshold leak flow value.

3. The method of claim 2 , wherein leak flow is determined over a predetermined time period.

4. The method of claim 3 , wherein the leak flow is determined based on a time constant of about 10 seconds.

5. The method of claim 1 , wherein the method is practiced with a CPAP device having two functional modes.

6. The method of claim 5 , wherein the first mode is a manual mode and the second mode is an automatic titration mode, and wherein:

in the manual mode, the test-fit pressure is the current set treatment pressure, and

in the automatic titration mode, the test-fit pressure is a percentile pressure of the prior treatment session.

7. The method of claim 6 , wherein the test-fit pressure is a base pressure if data from said prior treatment session is not available.

8. The method of claim 1 , wherein determining the mask-fit pressure includes sampling of pressure signals in a gas supply assembly associated with the mask.

9. The method of claim 8 , wherein the sampling of pressure signals occurs in a delivery tube of the gas supply assembly.

10. The method of claim 8 , wherein the sampling of pressure signals occurs at predetermined intervals.

11. The method of claim 10 , wherein sampling occurs at about 20 millisecond intervals.

12. The method of claim 8 , wherein the sampling of the pressure signals includes determining a flow of gas in the mask and generating a delivery pressure signal.

13. The method of claim 1 , further comprising varying at least one setting relating to test pressure intervals, test pressure period, and determined test pressure.

14. The method of claim 1 , wherein pressure data from said prior treatment session is available if the prior treatment pressure occurred for at least a predetermined time interval.

15. The method of claim 14 , wherein the predetermined time interval is about 3 hours.

16. A method for determining a mask-fit test pressure to be applied to a wearer's face by ventilatory assistance apparatus, wherein:

the mask-fit pressure is adaptively dependent on a prior pressure treatment session of the wearer,

determining the mask-fit pressure includes sampling of pressure signals in a gas supply assembly associated with the mask, and

the sampling of pressure signals occurs in a blower of the gas supply assembly.

17. A method for determining a mask-fit test pressure to be applied to a wearer's face by ventilatory assistance apparatus, wherein:

the mask-fit pressure is adaptively dependent on a prior pressure treatment session of the wearer,

determining the mask-fit pressure includes sampling of pressure signals in a gas supply assembly associated with the mask, and

determining the mask-fit pressure also includes processing the sampled pressure signals and producing a control signal based on the processed signals, wherein the control signal is provided to a motor to provide a determined treatment pressure.

18. The method of claim 17 , further comprising comparing a signal representative of actual delivery pressure with the control signal.

19. A method for determining mask-fit pressure to be applied to a wearer's mask by a continuous positive airway pressure apparatus having an automatic titration mode that delivers a flow of pressurized breathable gas to the wearer's mask, said method comprising:

measuring by a pressure sensor the mask pressure used by the wearer during a treatment session; and

determining a mask fit test pressure from the pressures used by the wearer during the treatment session, said mask-fit test pressure not being significantly different than pressures encountered in normal use of the wearer during the treatment session.